1. Field of the Invention
This invention relates generally to material handling apparatus and more specifically to harvesting apparatus used to pick up dried raisins placed upon flat paper sheets or trays disposed on the ground between rows of grapevines.
2. Description of the Prior Art
Raisin grapevines are arrayed in east to west rows with the rows being separated by a distance slightly greater than the wheel base of an ordinary tractor. These rows are typically level at the points adjacent vines themselves, however, there is a raised area known as a terrace between the rows. In the northern hemisphere the terraces are sloped such that the north sides are higher than the south sides. In this manner the maximum benefit of direct solar rays upon the terrace surface is obtained. This sloping terrace surface and the heat retentive properties of the grapevines typically cause the temperature between the rows on the terrace to be relatively higher than the temperature on a flat surface outside of the row.
Raisin grapes are ordinarily harvested in the following manner. Initially, the grapes are picked from the vines, removed from the stems and placed upon flat rectangular paper sheets, known as trays, which are placed on the terraces between the rows. The grapes are then allowed to dry on the trays in the sun until they have reached the proper stage of dehydration and are ready to be eaten. At this point laborers manually go through the rows and either fold the trays into rectangular packets or roll the trays into packets that resemble a cigarette in shape. Following this step the packets containing the raisins are typically picked up by mechanical means. At some point during the pick-up phase, the trays are removed and the raisins are deposited in boxes or other receptacles. From this point they are delivered to commercial packing houses.
Although this harvesting technique is utilized almost universally, and particularly on large ranches which use mechanical harvesters, there are several problems which typically arise. These problems include excessive labor expenditures, mechanical alignment difficulties on the harvesters and contamination of the harvested raisins with sand, dust and other particulate matter.
The step of manually taking the raisin laden trays and folding or rolling them in packets is highly labor intensive. In a large vineyard this step may consume a significant number of man hours. Furthermore, after the packets are picked up by mechanical harvesters they must be unrolled or unfolded such that the raisins may be removed therefrom. This step also requires significant labor expenditures.
A second difficulty is caused by the terracing between the rows of grapevines. Mechanical harvesters are typically drawn by tractors which have their wheels in the level areas adjacent to the grapevines themselves. However, the raisin laden trays are laid on the terrace surface which slopes from north to south. Consequently, in order to properly pick up the trays, the harvester pick-up mechanism must be angled off the vertical so as to match the slope of the terrace. This tilt must also be adjustable or it would be necessary to travel down all rows in the same direction. A rigidly mounted pick-up mechanism would necessitate extensive dead travel time back to the beginning of the next row, since the rows are frequently very lengthy, as well as requiring undue uniformity in the terrace slope angles.
Another difficulty associated with the use of mechanical harvesters lies in the necessity of having the raisins in closed containers at the time that they are picked up from the ground by the harvester. Some prior art mechanical harvesters, such as those disclosed in the U.S. patents issued to Garbedian, U.S. Pat. No. 3,587,814, and Hanson, U.S. Pat. No. 3,795,335, are designed so as to pick-up raisins contained in closed packets of sufficient thickness such that the grasping apparatus of these harvesters can propel the packets onto the conveyor. Furthermore, at the point that prior art harvesters pick-up the packets from the terrace, significant loss of raisins can be caused by the turbulent motion of the harvesters if the packets are insufficiently closed.
A further difficulty encountered in the harvesting of raisins is the contamination of the raisins by sand, dust and other small matter which is blown or otherwise deposited on the trays either during the drying period or the harvesting operation. Since the grapevines are deprived of water for a significant period of time prior to picking and harvesting the ground in the vineyards become very dry and dusty. During the period in which the raisin grapes are drying on the trays, sand and dust are deposited on the trays by the wind. This particulate matter is included in the packets when they are folded or rolled and is consequently delivered along with the raisins to the receptacles by mechanical harvesters of the prior art types.